The present invention relates to production of nanoparticles, especially nanoparticle composites, from powder agglomerates or powder aggregates.
The present invention relates more particularly to a process for producing preferably particulate composite materials, more particularly comprising generally inorganic and organic constituents, and also to the composite materials thus produced and their use.
The generation of composite materials in which the continuous phase is composed of an organic polymer or another meltable organic compound and the discontinuous phase, dispersed in the organic phase, is composed of generally inorganic or else organic particles represents a problem which in technical terms has not been solved in all of its component aspects.
On account of the large surface area of mesoscopic particles, these particles adhere to one another by electrostatic and/or van der Waals forces and form agglomerates and aggregates. These agglomerates and aggregates can be separated from one another again only by means of relatively high input of energy. In this case use is made, for example, of methods such as ultrasound; techniques with assistance from grinding media; roll mills; or various extruders. In many cases, however, the transfer of the energy from the dispersing assembly to the agglomerates or aggregates is limited in that the energy introduced is partly absorbed by the matrix particles and converted into heat. More particularly in melts and liquids of high viscosity this represents an enormous difficulty in the generation of homogeneous particle composites containing few or no agglomerates and/or aggregates.
Known from the prior art are processes, for example, in which organically modified particles (e.g., organophyllosilicates) are dispersed into polyolefins or polyamides, for example, with the use, for example, of chemical modifications, etc. In this case the modification leads to compatibilization with the matrix and so facilitates incorporation into the polymer. In other cases the synthesis of the particles takes place in such a way that, on account of their surface chemistry and surface charge, they are easily dispersed in polymer melts. In other cases still, the particles are generated in situ (e.g., by chemical precipitation of, for example, inorganic particles in organic media).
There are also processes known from the prior art with which micrometer-sized or else millimeter-sized particles can be dispersed into polymers, with disruption and dispersing of the agglomerates taking place by means of impact energy, for example.
U.S. Pat. No. 5,474,803 A describes the use of this process for generating polymer composites from two or more materials, a first component of relatively large particle diameter and relatively low softening point being surface-modified with a second component of higher softening point.
U.S. Pat. No. 6,403,219 B1 describes the generation of polymer composites by means of a growth reaction of acicular particles on the surface of a support material.
U.S. Pat. No. 6,090,440 A describes the generation of composites by exposure to impact forces and subsequent chemical reaction of the shell particles.
Common to all of the documents cited above is the generation of composites in which the materials used to modify the support are likewise composed of polymers or else must be constructed by means of a chemical reaction.
It is an object of the present invention to provide an efficiently operating process for the production or generation of preferably particulate composite materials. At the same time the process is more particularly to allow trouble-free dispersing of a discontinuous, organically or inorganically based phase in a continuous phase composed more particularly of at least one organic polymer and/or oligomer or of another meltable organic compound, and, advantageously, is intended to avoid at least largely, or else at least attenuate, the above-elucidated problems of the prior art.
To achieve the aforementioned object, the present invention proposes a process as disclosed herein. Further subject matter of the present invention are the composite materials obtainable by the process of the invention and their use. Also disclosed is a method of comminuting particle agglomerates or aggregates and of producing stable nanoparticles.